The present invention relates to axle assemblies for vehicles, and, more particularly, to steering arrangements for such axle assemblies.
Ground engaging work vehicles such as agricultural combines typically include a pair of axle assemblies, with each axle assembly including an axle, a pair of axle hubs at the respective longitudinal ends of the axle, and a pair or tires respectively mounted to the axle hubs. For steerable wheels, the axle hubs may be rotated relative to the axle about a kingpin such that the wheels are steered to a desired steering angle. Usually both wheels are steered with a power actuator such as a hydraulic cylinder, and the wheels are interconnected through a tie rod.
For agricultural vehicles, the tendency is for the vehicle to become larger and larger, so that the vehicle can pull and/or provide power to larger and heavier related equipment or implements. In the case of a combine, the size of the header or cutting platform mounted to the front of the combine tends to be larger over time, which increases power requirements. Grain storage capacity is also growing with higher threshing capacity, resulting in higher steering axle weights. Moreover, it is becoming more common to tow other implements behind the combine, such as biomass harvesters or related storage carts or wagons.
With larger combines, it may also be necessary or desirable to equip the combine with larger drive wheels and steering wheels. Such wheels provide a larger surface area contacting the ground, which in turn results in better traction, less soil compaction, less rolling resistance on wet soil, etc. However, in the case of the steering wheels, the use of larger wheels may also result in a smaller turning angle since the larger wheels can contact and potentially interfere with or damage the vehicle structure, such as frame members, sheet metal siding or housings, etc. A smaller turning angle causes a larger turning radius for the vehicle, which is not desirable. Additionally, road legislation in Europe is becoming more and more restrictive, requiring vehicle profiles to remain within certain width (3.5 m) and height (4 m) limits to drive without being accompanied by safety escort vehicles.
What is needed in the art is a steering arrangement for a large vehicle, such as a combine, which allows the use of large tires while at the same time retaining a tight turning radius for the vehicle.